Hydraulic pump or motor



De. 29, 1' I w, BRUNDAGE 3,551,081

HYDRAULIC PUMP OR MOTOR Filed 'Jan. 16,1969

4 Sheets-Sheet 1 INVENTOR. L ROBERT w BRUNDAGE 2 fw w 7a ATTORNEZ Dec. 29, 1970 R. w. BRUNDAGE 355L081 HYDRAULIC PUMP OR MOTOR Filed Jan 10, 1969 4 Sheets-Sheet 2 I NVEN TOR.

RQBERTW BRUNDAGE ATTORNEYS.

Filed Jan. 10, 1969 Dec. 29, 1970 R. w. BRUNDAGE HYDRAULIC PUMP 0R MOTOR ,lo h 49 751 ll FIG-.4 48 I 150 4 She ts-Sheet 3 INVENTOR. ROBERT W. BRUNDAGE W W W AT TOR N EYS.

Dec 29, 1970 BRUNDAGE 3,551,081

HYDRAULIC PUMP OR MOTOR Filed Jan. 10. 1969 4 Sheets-$heet 4.

FIGS

1 INVENTOR. ROBERT w BRUNDAGE ATTORNEYS.

United States Patent 3,551,081 HYDRAULIC PUMP OR MOTOR Robert Wesley Bruudage, St. Louis, M0., assiguor to Emerson Electric Co., St. Louis, Mo. Filed Jan. 10, 1969, Ser. No. 790,325 Int. Cl. F01c N US. Cl. 418-171 13 Claims ABSTRACT OF THE DISCLOSURE The hydraulic device has a shaft rotatably supported in the "housing by conventional sleeve bearings. A pair of internal gear pumping units are secured to the shaft with a disc on the shaft separating the two units. The high pressure chambers for the two units are on opposite sides of the shaft, thereby creating opposing moment couples which radically diminish the total bearing loads.

This invention relates to the art of hydraulic pumps or motors and, more particularly, to hydraulic pumps or motors which are intended for high pressure usage and which are large displacement units in the range of thirty horsepower and above.

The invention is particularly applicable to a hydraulic pump of the internal gear type and will be described with particular reference thereto, although it will be ap preciated that the invention is equally applicable to other types of hydraulic pumps or motors. As referred to hereinafter, the high and low pressures correspond to the discharge and inlet pressures, respectively, when the device is being used as a pump. If the invention is to be considered when applied to a motor, such high and low pressures will then become the inlet and discharge pressures, respectively.

Hydraulic pumps of the type to which this invention pertains are normally comprised of a housing and a shaft extending into and rotatably supported by suitable bearings in the housing. A pumping element which may comprise a pair of intermeshed, internally toothed and externally toothed gears may rotate with the shaft in a bearing surface eccentric to the axis of the shaft to definea plurality of increasing and decreasing volume pumpin'gichambers. Inlet and outlet manifolds communicating with these chambers are formed in the housing.

In pumps of this type, the high pressure in the chamhers is on one side of the shaft only and the low pressure is on the opposite side of the shaft. As a result, the forces created by such pressures are unsymmetrical and must be transmitted through the shaft and its supporting bearin'gs to the housing. Because of the magnitude of the forces under high pressure conditions, it has been conventional to support the shaft either in roller or ball Bearings of the precision type. This type of bearing support for the shaft has been generally satisfactory from the standpoint of withstanding the forces imposed on the shaft; however, these hearings are not only very expensive but also are relatively bulky. Although sleeve bearings are less expensive and are not as bulky as roller or ball bearings, they have not proven satisfactory in high pressure pumps or motors due to their inability to withstand the forces imposed on the shaft during normal operating conditions.

The present invention contemplates a new and improved hydraulic pump or motor, hereinafter generally referred to as a hydraulic device of the general type described, which overcomes the above referred to difficulties as well as others, and provides a high pressure, large displacement hydraulic device which is simple in construction and in which relatively inexpensive sleeve bearings can be used to support the shaft in the housing.

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In accordance with the present invention, a hydraulic device of the general type described is provided wherein two hydraulic units are operatively connected to the same shaft and are separated by a disc which is connected to and rotates with the shaft. The high pressure chamber for one of the hydraulic units is on one side of the shaft while the high pressure chamber for the other of the hydraulic units is positioned on the opposite side of the shaft. The radial forces created by the pressure in the chambers acting radially inwardly on the shaft create a moment couple on the shaft. In addition, the high pressure fluid in the chambers for each of the two hydraulic units acts against the face of the rotating disc to create a second moment couple which opposes the first moment couple to radically diminish the total loads imposed on the shaft bearings. In this manner, and if the appropriate structural relationships are maintained, it is possible theoretically to reduce the load on the shaft hearings to zero, thereby eliminating the need for expensive roller or ball bearings and permitting the use of conventional sleeve bearings.

The principal object of the invention is the provision of a new and improved hydraulic device of the general type described which is relatively inexpensive to manufacture but which is particularly adaptable for use as a high pressure, large displacement unit.

Another object of the invention is to provide an improved hydraulic device adapted for high pressure usage and which incorporates means for reducing the loads imposed on the shaft bearings.

Still another object of the invention is to provide an improved hydraulic device adapted for high pressure usage and in which conventional sleeve bearings may be employed to support the shaft in the housing.

Other objects and features of the invention will become more apparent upon a complete reading of the following description which, together with the attached drawings, shows but a preferred embodiment of the invention.

Referring now to the drawings wherein like reference numerals indicate like parts in the various views:

FIG. 1 is a cross-sectional view perpendicular to the neutral axis of a hydraulic device constructed in accordance with the principles of this invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

FIG. 3 is a sectional view taken along line 33 of FIG. 1.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 1.

FIG. 5 is a sectional view showing another embodiment of the invention.

Referring now in detail to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIG. 1 shows a pump indicated generally by the reference numeral 10 having generally cylindrical side walls 11 and end walls 12 and 13 which together cooperate to define a closed hydraulic chamber or cavity 14. A shaft 16 extends through the end wall 13 with the inner end 17 of the shaft being supported for rotation in a sleeve bearing 18 formed in the end wall 12. Similarly, sleeve bearing 19 supports the shaft 16 for rotation in the end wall 13.

A radially extending disc 20 is formed integral with the shaft 16 with the disc being positioned within the chamber 14. A first hydraulic unit indicated generally by the reference numeral 22 is positioned on one side of the disc in the chamber 14 with a second hydraulic unit indicated generally by the reference numeral v24 being positioned on the opposite side of the disc 20 within the chamber 14 Referring now to FIGS. 3 and 4, each of the hydraulic units will be more particularly described. Referring first to the unit 24, an externally toothed gear 26 is secured to the shaft 16 by a key 27 for rotation therewith. The gear 26 is surrounded by and adapted to intermesh with the teeth of an internally toothed gear 28. A bearing ring 29 is supported by the wall of the cavity 14 with the ring having an inner surface 30 which is eccentric to the outer surface 31.

The gear 28 may have a greater number, by one or more, of teeth than the gear 26 and is adapted to rotate on an axis which is eccentric to the axis of the shaft 16, thereby to cooperate with the teeth of the gear 26 to define a plurality of increasing and decreasing volume chambers 34 and 36. Both of these chambers are confined axially by the end wall 13 in sealing engagement with one axial side of the gears 26 and '28 and the sealing engagement between the other axial side of the gears and one side of the disc 20.

An inlet port 38 and an outlet port 40 in end wall 13 are in communication with inlet manifold 39 and outlet manifold 41, respectively. Both of these manifolds have a substantial arcuate extent and are continuously in communication with the increasing or decreasing volume chambers 34 and 36. The described hydraulic unit may be referred to, for convenience, as a Gerotor unit.

The other of the units 22 is substantially identical in construction to unit 24 and comprises an externally toothed internal gear 42 connected by a key 43 for rotation with the shaft 16. An internally toothed gear 44 surrounds the gear 42 with the gear 44 being supported for rotation in an eccentric bearing 46 carried by the walls of the cavity 14. The teeth of the two gears 42, 44 cooperate to define a plurality of increasing and decreasing volume chambers 48, 49 with the chambers being axially confined by the end wall 12 and the adjacent surface of the disc 20. An inlet port 50 and an outlet port 51 are formed in the end wall 12 and communicate with inlet manifold 52 and outlet manifold 53, respectively. Similar to the manifolds 39, 41, the manifolds 52, 53 are of substantial arcuate extent and are continuously in communication with the increasing or decreasing volume chambers 48, 49. However, contrasted with the manifolds 39, 41, the manifolds 52, 53-, are reversed in that the inlet manifold 52 is on the side of the shaft '16 opposite to the inlet manifold 39, and the outlet manifold 53 is positioned on the side of the shaft 16 opposite to the outlet manifold 41.

With the described arrangement it is theoretically possible to reduce the loads imposed on the sleeve bearings 18, 19 to zero. This becomes apparent from a force analysis of the system. Thus, ignoring the weight of the shaft and the gears which is imposed on the bearings and considering only the dynamic forces created by the hydraulic pressures as the device is operated, it is apparent that, at any given instant, the hydraulic pressures in the increasing and decreasing volume chambers 34, 36, 48 and 49 impose certain loads on the shaft. Referring first to the unit 24, at any given instant the hydraulic forces in that unit include the pressure of the fluid in the high and low pressure chambers acting radially inward on the inner gear and, hence, on the shaft. The sum of these forces may be integrated and represented by a single force, indicated by the arrow A, acting radially inwardly on the midline of the gear. At this same instant, a similar net radial force indicated by the arrow A is imposed on the midline of the gear 42 in the unit 22. However, since the high pressure chamber in unit 22 is on the side of the shaft 16 opposite to unit 24, the direction of the force A is opposite to the direction of the force A. Considering the forces which are imposed on the bearing 19 by the forces A and A, it is apparent that the force A acts through a moment arm which is substantially greater than the moment arm through which force A acts thus giving a net moment couple acting on the bearing 19 in a clockwise direction as viewed in FIG. 2. The reverse would be true of the forces acting on the bearing 18 wherein the moment arm of the force A exceeds the moment arm of the force A. When these two forces are added together, it is apparent that the moment couple created by the force A subtracts from the moment couple created by the force A, but, because of the larger moment arm through which the force A acts, a net moment couple in the clockwise direction is imposed on the bearing 18.

It is also apparent that the high pressure fluid in the two units 22, 24 also acts against the axial face of rotating disc 20 to produce forces which may be integrated and represented by forces B and B which act in opposite directions generally parallel to but radially spaced from the axis of the shaft 16. From an analysis of these forces, it will be understood that the two forces B and B cooperate to create a moment couple which, as viewed in FIG. 2, acts in a counterclockwise direction on shaft 16 and on bearings 18 and 19 and, hence, oppose the moment couples created by the forces A and A, thereby diminishing the load imposed on the bearings 18, 19.

Another approach to analyzing the effect of forces A, A, B and B is to sum the moments about the point P, which point is at the intersection of the centerline of shaft 16 and the midline of disc 20. With this analysis, it is apparent that the forces A, A combine to create a moment couple CA acting in a clockwise direction as viewed in FIG. 2. The forces B, B combine to create a moment couple CB which acts in a counterclockwise direction and, hence, opposes couple CA. Depending on the magnitude of couples CA and CB, it is possible to balance the loads on the shaft.

In addition to balancing the moment couples, it is also apparent that the forces tending to move shaft 16 either from left to right or up and down are also balanced. Thus, force A is equal in magnitude and opposite in direction to force A, thereby effectively neutralizing any tendency of the shaft to move laterally. Similarly, longitudinal movement of the shaft is prevented by the equal and opposing forces B, B.

It will be appreciated from the foregoing analysis that with the proper proportions of elements in the device, the shaft load at the bearing supports can theoretically be reduced to zero. For example, the magnitude of the radial forces A and A are dependent not only on the hydraulic pressure in the chambers but also the area of the gears 26, 42 against which the pressure acts. By decreasing the effective area of these gears as, for example, by reducing their width, the magnitude of the forces A and A can be reduced, thereby bringing the moment couple which they create into balance with the moment couple created by the forces B and B. Alternatively, the diameter of the gears and the disc may be increased thereby moving the area against which the forces B and B act radially outward, thus increasing the moment couple which they create. In this manner, the loads imposed on the bearings may be adjusted to insure that the least expensive bearing arrangement is employed for the particular application of the hydraulic device.

It will be understood that the moments on the disc 20 will be affected by such fluid pressure as may be present in the space 21 at the outer periphery of the disc; however, this factor has been ignored in the foregoing analysis since it will vary depending on the particular construction of the unit and whether, for example, the fluid in that space is directed back to suction or is disposed of in some other manner.

With the described arrangement, it is important that the disc be of sufificient width and strength to withstand the forces B and B without deflection. If deflection should occur in disc 20, not only will problems of leakage arise, but also, there may be a tendency for the disc to bind the gears of the pumping units. The relative strengths of disc and shaft is more fully explained in my Pat. 3,127,843, issued Apr. 7, 1964.

Referring now to the embodiment of FIG. 5, there is illustrated a modification of the hydraulic device, indicated generally by the reference numeral 60. Although the housing for the hydraulic device 60 may be the same as that shown in the embodiment of FIG. 1, a somewhat modified housing is illustrated. This housing employs a cylindrical sidewall 61 and end walls 62, 63 which together cooperate to define a closed hydraulic chamber or cavity 64. A shaft 66 extends through the end wall 62 with the inner end 67 of the shaft being supported in appropriate bearings such as antifriction roller bearings 68 in wall 63. Similarly, bearings 60 support the other end of the shaft for rotation in the end wall 62.

As in the embodiment of FIG. 1, the hydraulic device 60 employs a radially extending disc 70 which is formed integral with the shaft 66 and separates a pair of hydraulic units comprising internal gear pumps or motors 72, 74. A spacer ring 76 is positioned at the outer peripheral edge of the disc 70 and serves to space units 72, 74 within the chamber 64. Each of the units 72, 74 is of a construction which may be identical to that described in connection with the hydraulic units 22, 24.

An inlet port 78 is formed in the end wall 63 and, through fluid passages 79, 80, is in communication with each of the inlet manifolsd for the two hydraulic units 72, 74. The outlet manifold for each of the two hydraulic units are in communication with an outlet port, not shown.

The operation of the hydraulic device 60 is substantially the same as that described in connection with the hydraulic device of FIG. 1. However, it will be noted that the hydraulic unit 74 is substantially wider than the hydraulic unit 72. This differential in width or thickness of the hydraulic units may be on the order of one inch to one and one-half inches but may go as large as three to four inches if a unit of greater displacement is desired. However, as in the embodiment of FIG. 1, the high pressure chamber for the hydraulic unit 72 is positioned on the side of shaft 66 opposite to the high pressure chamber for the hydraulic unit 74. l

The arrangement of FIG. is particularly suitable for applications in which an external load is to be applied to the shaft 66. Thus, as discussed in connection with the embodiment of FIG. 1, it is theoretically possible to balance the loads on the shaft to reduce the loads to zero. However, when an external load is then applied to the shaft, it is possible that the shaft may tend to cock which would result in excessive rubbing and possible binding of the gears against the mating surfaces. The embodiment of FIG. 5 is adapted to avoid this occurrence. Thus, by making the one unit 74 larger than the other unit, it is possible to develop a relatively small but positive bearing load which acts in the same direction on both bearings. This positive loading of the bearings will cause the shaft 66 to maintain its alignment even in the presence of an external shaft load.

More specifically, the larger effective area of the high pressure chamber in hydraulic unit 74 results in a net load on the shaft 66 which tends to load the shaft in the same direction on both bearings 68, 69. For example, as shown in FIG. 5, assuming the high pressure chamber of the unit 74 is on the lower side of the shaft 66, the shaft 66 would be loaded in an upward direction into the bearings 68, 69. The magnitude of this loading of the bearings may be controlled by selecting the proper geometry and size of the hydraulic units 72, 74 and the disc 70, so that the moment couples, as described above, reduce the total bearing load to the desired level.

Assuming that the total bearing load is not reduced to zero but rather a positive bearing load is retained, it will be appreciated that this positive loading of the shaft into The bearings will counteract an external load applied to the shaft and will maintain the shaft in its properly aligned position.

It will be appreciated that modification and alterations in the disclosed invention will occur to those having ordinary skill in the art. For example, it will be readily appreciated that the disc need not be formed integrally with the shaft but may be secured for rotation therewith by a press fit. A keyed connection might also be employed; however, with such an arrangement, problems ofleakage may develop unless a shrink fit is used. It will' also be appreciated that additional pairs of hydraulic units may be employed with each pair having opposed inlet and outlet ports in the manner described above. Moreover, it is to be understood that the disclosed concept of balancing the forces imposed on the shaft bearings is applicable not only to gear pumps but may also be employed to advantage in other types of hydraulic devices such as a vane type device.

Having thus described my invention, I claim:

1. A hydraulic device comprised of:

a housing including end and side walls defining a hydraulic chamber in the interior thereof;

a shaft extending into said hydraulic chamber and,

rotatively supported by said walls;

first and second hydraulic units disposed in said chamber and operatively connected to said shaft for rotation therewith;

high pressure chambers for said units so disposed in relation to the shaft as to offset the radial loads thereby imposed on the shaft, and axially spaced apart so as to form a couple tending to turn the shaft endwise in a plane; and

means on the shaft reacting with said hydraulic units to form a second couple to oppose the first-named couple imposed on said shaft by the operation of said radial loads.

2. The device of claim 1 wherein said means include a disc rotatable with said shaft and exposed to the hydraulic pressures in said first and second hydraulic units.

3. The device of claim 2 wherein said disc is positioned between, said hydraulic units.

4. The device of claim 1 wherein each of said hydraulic units comprises internal and external means cooperating to define increasing and decreasing volume chambers;

disc means rotatable with said shaft;

said disc means being positioned along said shaft between said units with one side of said disc means being exposed to the pressures in the chambers of one of said units and the other side of said disc means being exposed to the pressures in the chambers of the other of said units.

5. The device of claim 4 wherein said shaft is supported in said housing by sleeve bearings.

'6. The device of claim 4 wherein said internal and external means comprise an internal gear pump;

first inlet and outlet manifold means defined in one end wall and communicating with the chambers of one of the pumps;

second inlrt and outlet manifold means defined in the other end wall and communicating with the chambers 0; the other of the pumps;

the outlet of one of one of the pumps being on one side of the shaft with the outlet of the other of the pumps being on the other side of the shaft. 1

7. The device of claim 1 wherein said means includes a disc effectively integral with said shaft and separating said hydraulic units whereby one axial face of said disc is exposed to the fluid pressures in one of said units and the other axial face of said disc is exposed to the fluid pressures in the other of said units.

8. The device of claim 1 wherein said units comprise internal gear devices of generally the same dimensional construction. 4

9. The device of claim 1 wherein each of said hydraulic units includes a high pressure chamber and a low pressure chamber,

a high pressure chamber of one of said units having an effective area exposed to fluid pressure that is greater than the elfective area of the high pressure chamber in the other of said units whereby a net force is generated which loads said shaft in a predetermined direction.

10. The device of claim 9, wherein said means includes a disc rotatable with said shaft and positioned between said hydraulic units with one side of said disc being exposed to the pressure in the chamber of one of said units and the other side of said disc being exposed to the pressure in the chamber of the other of said units,

the dimension of said disc being such that the moment couples generated by the pressures acting against said disc reduce the total load imposed on the shaft by the hydraulic units'to a predetermined level.

11. A hydraulic device comprised of:

a housing including end and side walls defining a hydraulic chamber in the interior thereof;

a shaft extending into said hydraulic chamber and rotatively supported by said walls;

first and second hydraulic units disposed in said chamber and operatively connected to said shaft for rotation therewith, said units imposing forces on the shaft which form a couple tending to rotate the shaft endwise; and 1 a disc effectively integral with the shaft between said imits whereby one axial face of said disc is exposed to the fluid pressures in one of said units and the 8 other axial face of said disc is exposed to the fluid pressures in the other of said units to form a second coupled which opposes the first-named couple.

12. The device of claim 6, wherein the disc means includes a disc element of sufficient width and strength to withstand the pressures to which it is exposed without deflection, whereby the internal and external means of said hydraulic units may rotate without binding.

13. The device of claim 4, wherein the disc means 10 includes a disc element of sufiicient width and strength to withstand the pressures to which it is exposed without deflection, whereby the internal and external means of said hydraulic units may rotate without binding.

References Cited UNITED STATES PATENTS CARLTON R. CROYLE, Primary Examiner W. J. GOODLIN, Assistant Examiner US. Cl. X.R. 

